Add Sidekiq::Queue#latency

Changes.md

@@ -2,7 +2,9 @@ HEAD
 -----------
 
 - Record the timestamp when jobs are enqueued. Add
-  Sidekiq::Stats::Job#enqueued_at to query the time. [mariovisic, #944]
+  Sidekiq::Job#enqueued\_at to query the time. [mariovisic, #944]
+- Add Sidekiq::Queue#latency - calculates diff between now and
+  enqueued\_at for the oldest job in the queue.
 
 2.12.0
 -----------

lib/sidekiq/api.rb

@@ -128,6 +128,14 @@ module Sidekiq
       Sidekiq.redis { |con| con.llen(@rname) }
     end
 
+    def latency
+      entry = Sidekiq.redis do |conn|
+        conn.lrange(@rname, -1, -1)
+      end.first
+      return 0 unless entry
+      Time.now.to_f - Sidekiq.load_json(entry)['enqueued_at']
+    end
+
     def each(&block)
       page = 0
       page_size = 50

lib/sidekiq/version.rb

@@ -1,3 +1,3 @@
 module Sidekiq
-  VERSION = "2.12.0"
+  VERSION = "2.12.1"
 end

test/test_api.rb

@@ -164,6 +164,7 @@ class TestApi < Minitest::Test
     it 'shows queue as empty' do
       q = Sidekiq::Queue.new
       assert_equal 0, q.size
+      assert_equal 0, q.latency
     end
 
     class ApiWorker
@@ -171,8 +172,8 @@ class TestApi < Minitest::Test
     end
 
     it 'can enumerate jobs' do
-      Time.stub(:now, Time.new(2012, 12, 26)) do
       q = Sidekiq::Queue.new
+      Time.stub(:now, Time.new(2012, 12, 26)) do
         ApiWorker.perform_async(1, 'mike')
         assert_equal ['TestApi::ApiWorker'], q.map(&:klass)
 
@@ -181,10 +182,13 @@ class TestApi < Minitest::Test
         assert_equal [1, 'mike'], job.args
         assert_equal Time.new(2012, 12, 26), job.enqueued_at
 
+      end
+
+      assert q.latency > 10_000_000
+
       q = Sidekiq::Queue.new('other')
       assert_equal 0, q.size
     end
-    end
 
     it 'can delete jobs' do
       q = Sidekiq::Queue.new